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  • 1
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    Ocean circulation modeling by use of radar altimeter data (1991)
    In:  CASI
    Details
    Publication Date: 2006-06-13
    Description: The project will investigate the use of radar altimetry (RA) data in the determination of the ocean circulation models. RA data will be used to verify prognostic experiments of the steady state and seasonal cycle of large-scale circulation models and the statistical steady state of eddy-resolving models. The data will serve as initial and update conditions in data assimilation experiments and as constraints in inverse calculations. The aim of the project is a better understanding of ocean physics, the determination and mapping of ocean currents, and a contribution to the establishment of ocean circulation models for climate studies. The goal of the project is to use satellite radar altimetry data for improving our knowledge of ocean circulation both in a descriptive sense and through the physics that govern the circulation state. The basic tool is a series of ocean circulation models. Depending on the model, different techniques will be applied to incorporate the RA data.
    Keywords: OCEANOGRAPHY
    Type: JPL, TOPEX(Poseidon Science Investigations Plan; p 103-104
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  • 2
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    The modification of X and L band radar signals by monomolecular sea slicks (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: One methyl oleate and two oleyl alcohol surface films were produced on the surface of the North Sea under comparable oceanographic and meteorological conditions in order to investigate their influence on X and L band radar backscatter. Signals are backscattered in these bands primarily by surface waves with lengths of about 2 and 12 cm, respectively, and backscattered power levels in both bands were reduced by the slicks. The reduction was larger at X band than at L band, however, indicating that shorter waves are more intensely damped by the surface films. The oleyl alcohol film caused greater attenuation of short gravity waves than the film of methyl oleate, thus demonstrating the importance of the physicochemical properties of films on the damping of wind-generated gravity capillary waves. Finally, these experiments indicate a distinct dependence of the degree of damping on the angle between wind and waves. Wind-generated waves traveling in the wind direction are more intensely damped by surface films than are waves traveling at large angles to the wind.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 9817-982
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  • 3
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    Variation of the microwave brightness temperature of sea surfaces covered with mineral and monomolecular oil films (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: ENVIRONMENT POLLUTION
    Type: (ISSN 0196-2892)
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  • 4
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    On the detection of underwater bottom topography by imaging radars (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A theoretical model which explains basic properties of radar imaging of underwater bottom topography in tidal channels is presented. The surface roughness modulation is described by weak hydrodynamic interaction theory in the relaxation time approximation. In contrast to previous theories on short wave modulation by long ocean waves, a different approximation is used to describe short wave modulation by tidal flow over underwater bottom topography. The modulation depth is proportional to the relaxation time of the Bragg waves. The large modulation of radar reflectivity observed in SEASAT-SAR imagery of sand banks in the Southern Bight of the North Sea are explained by assuming that the relaxation time of 34 cm Bragg waves is of the order of 30-40 seconds.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Frontiers of Remote Sensing of the Oceans and Troposphere from Air and Space Platforms; p 403-413
    Format: application/pdf
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  • 5
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    The effect of monomolecular surface films on the microwave brightness temperature of the sea surface (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is pointed out that monomolecular surface films of biological origin are often encountered on the ocean surface, especially in coastal regions. The thicknesses of the monomolecular films are of the order of 3 x 10 to the -9th m. Huehnerfuss et al. (1978, 1981) have shown that monomolecular surface films damp surface waves quite strongly in the centimeter to decimeter wavelength regime. Other effects caused by films are related to the reduction of the gas exchange at the air-sea interface and the decrease of the wind stress. The present investigation is concerned with experiments which reveal an unexpectedly large response of the microwave brightness temperature to a monomolecular oleyl alcohol slick at 1.43 GHz. Brightness temperature is a function of the complex dielectric constant of thy upper layer of the ocean. During six overflights over an ocean area covered with an artificial monomolecular alcohol film, a large decrease of the brightness temperature at the L-band was measured, while at the S-band almost no decrease was observed.
    Keywords: OCEANOGRAPHY
    Type: International Journal of Remote Sensing; 3; Oct
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  • 6
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    The damping of ocean surface waves by a monomolecular film measured by wave staffs and microwave radars (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Open ocean and wave tank experiments were carried out with the aim of studying the damping of capillary and gravity waves by a monomolecular film. These films of biogenic origin influence air-sea interaction processes and thereby affect the use of remote sensing techniques in oceanography. Measurement was carried out by wave staffs, by a coherent X band microwave scatterometer mounted on a sea-based platform, and by an incoherent K band microwave scatterometer carried by an aircraft under moderate wind conditions. A wave attenuation of about 40-60% is observed in the frequency range between 3.2 and 16 Hz. Tank experiments show that a direct influence of oleyl alcohol surface films on wave damping is confined to frequencies equal to or greater than 2 Hz; a further indirect effect of films on the damping of ocean waves in the frequency range between 0.12 and 0.7 Hz (by modifying the wind input and wave-wave interaction mechanisms) is also indicated
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research; 86; Jan. 20
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  • 7
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    Measurements at 13.9 GHz of the radar backscattering cross section of the North Sea covered with an artificial surface film (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The reduction of the Ku-band (13.9 GHz) normalized radar cross section (NRCS) by an artificial monomolecular surface film (oleyl alcohol) on the sea surface was measured in the North Sea during the 1975 Joint North Sea Wave Project, JONSWAP 75 experiment. The aim of the surface film experiment was to simulate natural surface films which often occur on the ocean surface and are produced by plankton or fish. NRCS measurements were obtained from an aircraft at incidence angles of 41 deg and 47 deg at vertical and horizontal polarizations. For winds between 3.5 and 4.4 m/sec the maximum measured reduction was 7.3 plus or minus 3.5 dB relative to the mean. In-situ measurements showed that the oleyl alcohol film reduced the surface tension from 74 to 43 dyne/cm.
    Keywords: OCEANOGRAPHY
    Type: Radio Science; 13; Nov
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  • 8
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    Measurement of ocean wave heights using the Geos 3 altimeter (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Radar altimeter signals transmitted from the low-orbiting satellite Geos 3 were analyzed for two selected orbits over high seas associated with hurricane 'Caroline' in the Gulf of Mexico and a North Atlantic storm. The measured values of significant wave height are in reasonable agreement with surface measurements, provided that the altimeter data are properly edited. The internal consistency of estimated wave heights for the North Atlantic storm, a standard deviation of 0.6 m or less, and the good agreement with surface truth lend credence to the method. A statistical analysis of the pulse slope variation gives estimated values of significant wave height within + or - 1 m of the true values 75% of the time for spatial averaging over 70 km.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research; 83; Oct. 20
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  • 9
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    The modulation of the radar backscattering cross section by long ocean waves (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The modulation transfer function which relates the backscattered microwave power to the long ocean wave field was measured in the North Sea during JONSWAP 75. Results from this tower experiment with an X-band scatterometer are presented and compared with the two-scale wave model (relaxation-time model).
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: International Symposium on Remote Sensing of Environment; Apr 20, 1978 - Apr 26, 1978; Manila; Philippines
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  • 10
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    Satellite observations of oceanic eddies around Africa (2014)
    Springer
    In:  In: Remote Sensing of the African Seas. , ed. by Barale, V. and Gade, M. Springer, Dordrecht, Netherlands, pp. 205-231. ISBN 978-94-017-8007-0
    Details
    Publication Date: 2015-03-05
    Description: Oceanic eddies having scales from several hundred meters to several hundred kilometers are ubiquitous phenomena in the World’s ocean. This became evident only after they could be observed from satellites and space shuttles. Here we present several images taken in different spectral bands which show signatures of eddies of different spatial scales in sea areas around Africa. In particular, we present a series of satellite images showing the propagation of a small-scale cyclonic (cold) eddy generated at Cap-Vert at the coast of Senegal into the open ocean. We show that this small-scale eddy transported nutrients from the Senegal upwelling region westward into the oligotrophic North Atlantic thus giving rise to enhanced chlorophyll-a concentration there. Since eddies are also areas of high fish population, knowledge of their position and properties is of great importance for fishery.
    Type: Book chapter , NonPeerReviewed
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